A study of distributed Bragg reflector on LiNbO3 waveguide

• Main Authors: Shang-Da Yang, 楊尚達
• Other Authors: Way-Seen Wang
• Format: Others
• Language: en_US
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/09187502986217963852

碩士 === 國立臺灣大學 === 光電工程學研究所 === 87 === Distributed Bragg reflector (DBR) is found to be suitable as the cavity mirror of an erbium-doped LiNbO3 waveguide laser, because it may provide sufficiently high reflectivity, narrow bandwidth, and is capable of monolithically integrating with other integrated optical devices. Whereas, the traditional surface-relief DBR produced by etching grooves on the LiNbO3 waveguide usually exhibits very weak mode-index modulation, and therefore limited reflectivity. Significant improvements could be carried out if the Si-on-LiNbO3 structure is used, and the periodic corrugations are then introduced on the surface of silicon overlay. In this work, the novel features of the corrugated high index overlay (CHIO) DBR are theoretically investigated by the coupled-mode equations. Simulation results indicate that the coupling strength is sensitive to the Si-layer thickness, which is attributed to the transition of dominant mode intensity distribution from the LiNbO3 waveguide region up to the Si-layer. The optimum structural parameters for maximum effective reflectivity could be obtained after the insertion loss caused by mode profile mismatch is also taken into account. From which, a 3mm uniform DBR with peak reflectivity of 99.5% and bandwidth of 0.4nm could be anticipated. Finally, the spectral characteristics of various aperiodic CHIO DBR''s will be analyzed in terms of the fundamental matrix method, which demonstrate a wide variety of practical applications.